Designs

25 pages, 4947 KB

Open AccessArticle

An Application of Reinforcement Learning to the Optimal Design of Road Vehicle Suspension Systems

by Lorenzo De Santanna, Riccardo Malacrida, Gianpiero Mastinu and Massimiliano Gobbi

Designs 2025, 9(5), 108; https://doi.org/10.3390/designs9050108 - 12 Sep 2025

This study investigates the application of Multi-Objective Reinforcement Learning–Dominance-Based (MORL–DB) method to the optimal design of complex mechanical systems. The MORL–DB method employs a Deep Deterministic Policy Gradient (DDPG) agent to identify the optimal solutions of the multi-objective problem. By adopting the k [...] Read more.

This study investigates the application of Multi-Objective Reinforcement Learning–Dominance-Based (MORL–DB) method to the optimal design of complex mechanical systems. The MORL–DB method employs a Deep Deterministic Policy Gradient (DDPG) agent to identify the optimal solutions of the multi-objective problem. By adopting the k-optimality metric, which introduces an optimality ranking within the Pareto-optimal set of solutions, a final design solution can be chosen more easily, especially when considering a large number of objective functions. The method is successfully applied to the elasto-kinematic optimisation of a double wishbone suspension system, featuring a multi-body model in ADAMS Car. This complex design task includes 30 design variables and 14 objective functions. The MORL–DB method is compared with two other approaches: the Moving Spheres (MS) method, specifically developed for spatial design tasks, and the genetic algorithm with k-optimality-based sorting (KEMOGA). Comparative results show that the MORL–DB method achieves solutions of higher optimality while requiring significantly fewer objective function evaluations. The results demonstrate that the MORL–DB method is a promising and sample-efficient alternative for multi-objective optimisation, particularly in problems involving high-dimensional design spaces and expensive objective function evaluations. Full article

(This article belongs to the Collection Editorial Board Members’ Collection Series: Designs of New Generation Vehicles)

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16 pages, 3953 KB

Open AccessArticle

3D-Printed Prosthetic Solutions for Dogs: Integrating Computational Design and Additive Manufacturing

by Jeremy Sarpong, Khalil Khanafer and Mohammad Sheikh

Designs 2025, 9(5), 107; https://doi.org/10.3390/designs9050107 - 7 Sep 2025

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Abstract

This study investigates the mechanical performance of two prosthetic forelimb designs for dogs—one with a solid structure and the other with a perforated structure—using Finite Element Analysis (FEA). Both models were analyzed under static loading conditions representing approximately 60% of a dog’s body [...] Read more.

This study investigates the mechanical performance of two prosthetic forelimb designs for dogs—one with a solid structure and the other with a perforated structure—using Finite Element Analysis (FEA). Both models were analyzed under static loading conditions representing approximately 60% of a dog’s body weight, the typical load borne by the forelimbs. The prosthetics were modeled with ABS plastic, a widely used 3D printing material, and evaluated for Von Mises stress, total deformation, elastic strain, and factor of safety. The analysis showed that both models remained within the elastic limit of the material, indicating that no permanent deformation would occur under the applied loads. The Solid Model demonstrated a significantly higher factor of safety (14) and lower deformation, confirming its structural strength but also highlighting excessive rigidity, increased material use, and higher cost. In contrast, the Perforated Model exhibited slightly higher localized stresses and a lower factor of safety (3.01), yet it still met essential safety requirements while providing greater compliance, flexibility, and material efficiency. These attributes are desirable for comfort, adaptability, and practicality in veterinary applications. Although its long-term durability requires further evaluation, the Perforated Model strikes a more effective balance between safety, comfort, and sustainability. Based on these findings, the perforated design is considered the more suitable option for canine prosthetic development. Future work will extend the analysis to dynamic loading scenarios, such as walking and running, to better simulate real-world performance. Full article

(This article belongs to the Special Issue Design Process for Additive Manufacturing)

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18 pages, 3818 KB

Open AccessArticle

Effect of Cross-Section Designs on Energy Absorption of Mechanical Metamaterials

by Xinnian Wang, Sina Rastegarzadeh, Yayue Pan and Jida Huang

Designs 2025, 9(5), 106; https://doi.org/10.3390/designs9050106 - 7 Sep 2025

Viewed by 136

Abstract

Numerous studies have examined various geometric designs in cellular structures, yet the role of cross-sectional geometry remains underexplored. Cross-sections significantly influence the effective material properties of architected materials, where stress concentrations at junctions can reduce structural strength. This study investigates how different cross-sections [...] Read more.

Numerous studies have examined various geometric designs in cellular structures, yet the role of cross-sectional geometry remains underexplored. Cross-sections significantly influence the effective material properties of architected materials, where stress concentrations at junctions can reduce structural strength. This study investigates how different cross-sections affect energy absorption efficiency in both bending- and stretching-dominated cellular structures. Five classes of lattice structures, each designed with four distinct cross-sections, were fabricated using a custom stereolithography printer. Mechanical performance—specifically energy absorption and energy absorption efficiency—was evaluated through physical simulation and experimental testing. The results show that selecting optimal cross-sections can enhance yield stress by an average of 35% for cubic, 39% for BCC, 22% for BCCZ, and 41% for FCC structures. These findings demonstrate the critical impact of cross-sectional geometry on mechanical behavior. Both experimental and finite element analysis-based homogenization approaches were employed to validate results. The study proposes cross-section design guidelines aimed at optimizing strength-to-weight ratios, offering valuable insights for the development of high-performance mechanical metamaterials. Full article

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17 pages, 6935 KB

Open AccessArticle

Improving the Torque of a Paddle Mini-Hydropower Plant Through Geometric Parameter Optimization and the Use of a Current Amplifier

by Almira Zhilkashinova, Igor Ocheredko and Madi Abilev

Designs 2025, 9(5), 105; https://doi.org/10.3390/designs9050105 - 4 Sep 2025

Viewed by 286

Abstract

In the presented work, the main challenge of small hydropower plants—converting low river flow velocities into high generator rotations—is investigated. It was established that applying the flow acceleration effect during interaction with surfaces makes it possible to increase the power output of a [...] Read more.

In the presented work, the main challenge of small hydropower plants—converting low river flow velocities into high generator rotations—is investigated. It was established that applying the flow acceleration effect during interaction with surfaces makes it possible to increase the power output of a small hydropower plant by up to 25%, which corresponds to the level of an innovative solution. Stationary flow amplifiers and their influence on the dynamic interaction of blades were studied. It was revealed that the use of the amplification effect in paired configurations contributes to achieving a multiplicative effect. The potential of small hydropower plants was analytically evaluated, taking into account their dimensions and gear systems. The study was carried out using the method of computational fluid dynamics (CFD), which enables the modeling of complex hydrodynamic processes. Based on the developed three-dimensional model of the object and its discretization into a computational mesh, boundary conditions were set, and the finite volume method was applied to solve the Navier–Stokes equations. To account for turbulent flows, the k-epsilon turbulence model was employed. Full article

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17 pages, 1914 KB

Open AccessSystematic Review

Fatigue Resistance of RAP-Modified Asphalt Mixes Versus Conventional Mixes Using the Indirect Tensile Test: A Systematic Review

by Giuseppe Loprencipe, Laura Moretti and Mario Saltaren Daniel

Designs 2025, 9(5), 104; https://doi.org/10.3390/designs9050104 - 1 Sep 2025

Viewed by 407

Abstract

The use of Reclaimed Asphalt Pavement (RAP) in asphalt mixtures offers environmental and economic advantages by reducing reliance on virgin aggregates and minimizing construction waste. However, the aged binder in RAP increases mixture stiffness, which can compromise fatigue resistance. This systematic review evaluates [...] Read more.

The use of Reclaimed Asphalt Pavement (RAP) in asphalt mixtures offers environmental and economic advantages by reducing reliance on virgin aggregates and minimizing construction waste. However, the aged binder in RAP increases mixture stiffness, which can compromise fatigue resistance. This systematic review evaluates the influence of RAP content on fatigue performance compared to conventional mixtures, with a focus on the Indirect Tensile Test (IDT) as the primary assessment method. Following the parameters of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, five studies published between 2014 and 2024 were identified through searches in Web of Science, ScienceDirect, ASCE, and Scopus. Study quality was assessed using the Cochrane Risk of Bias tool. The results indicate that although RAP enhances rutting resistance, higher contents (>30%) often lead to reduced fatigue performance due to binder hardening and reduced mixture flexibility. The incorporation of rejuvenators—such as heavy paraffinic extracts—and modifiers, including high-modulus agents, polymers, and epoxy binders, can partially restore aged binder properties and improve performance. Sustainable innovations, such as lignin-based industrial by-products and warm-mix asphalt technologies, show promise in balancing mechanical performance with reduced environmental impact. Variability in material sources, modification strategies, and test protocols limits direct comparability among studies, underscoring the need for standardized evaluation frameworks. Overall, this review highlights that optimizing RAP content and selecting effective rejuvenation or modification strategies are essential for achieving durable, cost-effective, and environmentally responsible asphalt pavements. Future research should integrate advanced laboratory methods with performance-based design to enable high RAP utilization without compromising fatigue resistance. Full article

(This article belongs to the Special Issue Sustainable Construction: Innovations in Design, Engineering, and the Circular Economy)

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14 pages, 1870 KB

Open AccessArticle

Development and Mechanical Evaluation of a Stent Graft for Endovascular Aneurysm Repair Using Finite Element Modeling

by Athanasios Konstantakopoulos, Nikolaos Kladovasilakis and Georgios E. Stavroulakis

Designs 2025, 9(5), 103; https://doi.org/10.3390/designs9050103 - 1 Sep 2025

Viewed by 417

Abstract

An abdominal aortic aneurysm (AAA) poses a significant risk of arterial wall rupture, which critically endangers the patient’s life. To address this condition, an endovascular aneurysm repair (EVAR) is required, involving the insertion and expansion of a stent-graft within the aorta, to support [...] Read more.

An abdominal aortic aneurysm (AAA) poses a significant risk of arterial wall rupture, which critically endangers the patient’s life. To address this condition, an endovascular aneurysm repair (EVAR) is required, involving the insertion and expansion of a stent-graft within the aorta, to support and isolate the weakened vessel wall. In this context, this article aims to approach the problem from a mechanical perspective and to simulate the expansion and deployment procedure realistically, utilizing the Finite Element Analysis (FEA). The process initiates with the computation evaluation of the aortic structure in order to identify critical regions of stress and strain in an aneurysmatic aortic region. Then, a customized 3D-designed stent graft model was developed for the aorta and positioned properly. Applying all the necessary boundary conditions, a complex nonlinear FEA was conducted until the stent-graft expanded radially, reaching a final diameter 25% larger than the aorta’s vessel wall while withstanding mean stress and strain values close to 400 MPa and 1.5%, respectively. Finally, the mechanical behavior of the stent-graft and its interaction with the internal aortic wall, during the expansion process, was evaluated, and the extracted results were analyzed. Full article

(This article belongs to the Special Issue Advanced Design Methodologies for Additive Manufacturing in Patient-Specific Medical Solutions)

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24 pages, 1013 KB

Open AccessReview

Smart Design Aided by Mathematical Approaches: Adaptive Manufacturing, Sustainability, and Biomimetic Materials

by Antreas Kantaros, Theodore Ganetsos, Evangelos Pallis and Michail Papoutsidakis

Designs 2025, 9(5), 102; https://doi.org/10.3390/designs9050102 - 1 Sep 2025

Viewed by 503

Abstract

The increased importance of sustainability imperatives has required a profound reconsideration of the interaction between materials, manufacturing, and design fields. Biomimetic smart materials such as shape-memory polymers, hydrogels, and electro-active composites represent an opportunity to combine adaptability, responsiveness, and ecological intelligence in systems [...] Read more.

The increased importance of sustainability imperatives has required a profound reconsideration of the interaction between materials, manufacturing, and design fields. Biomimetic smart materials such as shape-memory polymers, hydrogels, and electro-active composites represent an opportunity to combine adaptability, responsiveness, and ecological intelligence in systems and products. This work reviews the confluence of such materials with leading-edge manufacturing technologies, notably additive and 4D printing, and how their combining opens the door to the realization of time-responsive, low-waste, and user-adaptive design solutions. Through computational modeling and mathematical simulations, the adaptive performance of these materials can be predicted and optimized, supporting functional integration with high precision. On the basis of case studies in regenerative medicine, architecture, wearables, and sustainable product design, this work formulates the possibility of biomimetic strategies in shifting design paradigms away from static towards dynamic, from fixed products to evolvable systems. Major material categories of stimuli-responsive materials are systematically reviewed, existing 4D printing workflows are outlined, and the way temporal design principles are revolutionizing production, interaction, and lifecycle management is discussed. Quantitative advances such as actuation efficiencies exceeding 85%, printing resolution improvements of up to 50 μm, and lifecycle material savings of over 30% are presented where available, to underscore measurable impact. Challenges such as material scalability, process integration, and design education shortages are critically debated. Ethical and cultural implications such as material autonomy, transparency, and cross-cultural design paradigms are also addressed. By identifying existing limitations and proposing a future-proof framework, this work positions itself within the ongoing discussion on regenerative, interdisciplinary design. Ultimately, it contributes to the advancement of sustainable innovation by equipping researchers and practitioners with a set of adaptable tools grounded in biomimicry, computational intelligence, and temporal design thinking. Full article

(This article belongs to the Collection Editorial Board Members’ Collection Series: Biomaterials Design)

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25 pages, 14188 KB

Open AccessArticle

Assessment of Accuracy in Geometry Reconstruction, CAD Modeling, and MEX Additive Manufacturing for Models Characterized by Axisymmetry and Primitive Geometries

by Paweł Turek, Piotr Bielarski, Alicja Czapla, Hubert Futoma, Tomasz Hajder and Jacek Misiura

Designs 2025, 9(5), 101; https://doi.org/10.3390/designs9050101 - 28 Aug 2025

Viewed by 437

Abstract

Due to the rapid advancements in coordinate measuring systems, data processing software, and additive manufacturing (AM) techniques, it has become possible to create copies of existing models through the reverse engineering (RE) process. However, the lack of precise estimates regarding the accuracy of [...] Read more.

Due to the rapid advancements in coordinate measuring systems, data processing software, and additive manufacturing (AM) techniques, it has become possible to create copies of existing models through the reverse engineering (RE) process. However, the lack of precise estimates regarding the accuracy of the RE process—particularly at the measurement, reconstruction, and computer-aided design (CAD) modeling stages—poses significant challenges. Additionally, the assessment of dimensional and geometrical errors during the manufacturing stage using AM techniques limits the practical implementation of product replicas in the industry. This paper provides an estimation of the errors encountered in the RE process and the AM stage of various models. It includes examples of an electrical box, a lampshade for a standing lamp, a cover for a vacuum unit, and a battery cover. The geometry of these models was measured using a GOM Scan 1 (Carl Zeiss AG, Jena, Germany). Following the measurement process, data processing was performed, along with CAD modeling, which involved primitive detection, profile extraction, and auto-surface methods using Siemens NX 2406 software (Siemens Digital Industries, Plano, TX, USA). The models were produced using a Fortus 360-mc 3D printer (Stratasys, Eden Prairie, MN, USA) with ABS-M30 material. After fabrication, the models were scanned using a GOM Scan 1 scanner to identify any manufacturing errors. The research findings indicated that overall, 95% of the points representing reconstruction errors are within the maximum deviation range of ±0.6 mm to ±1 mm. The highest errors in CAD modeling were attributed to the auto-surfacing method, overall, 95% of the points are within the average range of ±0.9 mm. In contrast, the lowest errors occurred with the detect primitives method, averaging ±0.6 mm. Overall, 95% of the points representing the surface of a model made using the additive manufacturing technology fall within the deviation range ±0.2 mm on average. The findings provide crucial insights for designers utilizing RE and AM techniques in creating functional model replicas. Full article

(This article belongs to the Special Issue Design Process for Additive Manufacturing)

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14 pages, 1425 KB

Open AccessArticle

Design-Informed Evaluation and Fretting Damage Mapping of Additive-Manufactured Ti-6Al-4V Components

by Ahmad Sadeghian and Saeed Adibnazari

Designs 2025, 9(5), 100; https://doi.org/10.3390/designs9050100 - 25 Aug 2025

Viewed by 442

Abstract

This paper experimentally investigates the fretting fatigue behavior of metal additive-manufactured Ti-6Al-4V alloy specimens fabricated using the selective laser melting (SLM) method, focusing on damage characterization and fatigue life assessment. Based on the ASTM E466 standard, the test components were manufactured using metal [...] Read more.

This paper experimentally investigates the fretting fatigue behavior of metal additive-manufactured Ti-6Al-4V alloy specimens fabricated using the selective laser melting (SLM) method, focusing on damage characterization and fatigue life assessment. Based on the ASTM E466 standard, the test components were manufactured using metal 3D printing technology. Fretting fatigue tests were conducted under varying axial stress levels and contact loads, followed by microscopic examinations using scanning electron microscopy (SEM) to analyze damage mechanisms. A fretting map was developed based on SEM observations, providing insights into damage evolution under different loading conditions. These findings contribute to a better understanding of the relationship between fretting fatigue parameters and failure mechanisms. The developed fretting map and experimental observations provide a foundation for further studies aimed at enhancing the fretting fatigue life assessment of standard specimens for different test parameters. Finally, this paper includes design-oriented evaluation frameworks that can guide engineers in integrating AM components into safety-critical systems under fretting fatigue conditions. Full article

(This article belongs to the Section Mechanical Engineering Design)

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Designs, Volume 9, Issue 5 (October 2025) – 9 articles

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